In producing canned foods, the filled cans or jars must be heated to prevent spoilage. In commercial operations the cans or jars of food are often loaded within a retort crate; the loaded retort crate is then placed within a heated retort for a specified period of time. Retort crates are typically heavy ferrous cylindrical containers having a lower edge upon which a movable bottom rests. The retort crates have no top. The bottom and sides of the crates are usually perforated to allow the hot water within the retort to flow freely around the containers in the crates.
In the past, one machine has been used for loading layers of jars into the crate and another used for unloading of the jars from the crate after they have been heated in the retort. Such a duplication of equipment is costly and takes a significant amount of valuable floor space in the plant.
Operationally, retort crate loaders load jars into a retort crate from a moving conveyor. At the end of the moving conveyor is a dead plate. A jar clamp is situated above the dead plate. The conveyor moves the jars past the dead plate and into the retort crate where they rest upon a slip sheet or divider which is placed between the layers of jars. After a new layer of jars is filled, the clamp is brought down upon the jars resting on the dead plate. These jar clamps have typically used magnets to hold the jars resting near the edge of the dead plate in place while the newly loaded layer of jars is indexed down one level. However, during recent years the thickness of the metal cap has been reduced to such an extent that the magnets are often no longer effective to securely hold the jars. Therefore, jars which hang over the outer edge of the dead plate often fall into the new layer of jars when the layer is lowered. Since there is generally not room for it, the extra jar, known as a leaner, must be removed by the operator. Such operator intervention causes a break in the normal flow and thus increases the time required to load the jars.
Another problem with the prior art retort crate loaders arises when a jar hangs substantially over the outer end of the dead plate. However, because the lower edge of the jar is rounded, when the newly loaded layer of jars is lowered, this imperfectly clamped jar also becomes a "leaner". Therefore, the operator must again interrupt the flow to accommodate the leaner.
Presently, retort crate loaders require that the operator manually control the vertical index down motion. When doing so the operator lowers the jars past the desired position so that they can be jogged several times, by raising and lowering the jars, to properly settle the jars in place. This is quite time consuming since the operator must hunt for the proper level.